Questions tagged [power-electronics]

Refers to the conversion of electric power by using solid state components such as semiconductors. Can also generally apply to the field of electrical engineering which works with power electronics.

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78
votes
11answers
27k views

Where does electricity go after being used?

For a very long time I have been wondering, where does electricity go after being used? When I use my tablet it runs from a battery. Where does the power go?
34
votes
2answers
10k views

Weird resistor with dots around it on the schematic

I was looking through the LTC4041 datasheet and saw this: The 10mOhm resistor with the two nodes really close to it - is that a "special" resistor or something? Why have they drawn it like that?
33
votes
8answers
5k views

Why do devices stop operating properly in extreme cold?

I have noticed that a lot of smart phones say that they won't operate under -4 degrees F (-20 degrees C). Can anyone explain to me what happens when the phones get cold that stops them from operating?
33
votes
3answers
6k views

Why does power dip during a lightning storm?

If lightning were to strike power lines, wouldn't you expect it to increase the power, and hence your room lights get brighter? Why do they go dim for 1 second at a time?
26
votes
4answers
3k views

Spacecraft Power Supply Frequency

I know that aircraft sometimes employ a 400Hz AC system to save weight on transformers, so I'd imagine that spacecraft might employ a similar technique. I'm wondering if anyone in the aerospace field ...
19
votes
10answers
6k views

Are all electrical sockets of my house in the same phase?

Most countries use AC power that is supplied to each house. This AC power is in the form of a sine wave. Suppose I have 2 electrical power sockets in two rooms that are at the opposite ends of my ...
15
votes
3answers
37k views

What is Overmodulation?

The Wikipedia article is very short and doesn't explain the concept very well, and there aren't any other sites that I can find that give a simple explanation. What does it mean by 100% modulation? I ...
15
votes
5answers
1k views

Voltage regulator from first principles - why is power dumped in the transistor?

I'm trying to further my understanding of electronics, so I decided to try to design a fixed voltage regulator capable of supplying an amp or so. I put this together from first principles without ...
14
votes
2answers
3k views

IGBT vs. Power MOSFET for switching applications. Where to draw the line?

For lower breakdown voltages, a power MOSFET is clearly the device to go for, in view of its higher efficiency, higher commutation speed and lower price. Where should the line be drawn, upwards of ...
14
votes
3answers
945 views

Why an electrician wiring error could make a PC's USB shield be at 120V when it should be grounded

I almost had a serious electrical accident last week when I was trying to use an oscilloscope to test out a circuit a student had built. I had the scope plugged into a floor outlet, and the circuit ...
14
votes
1answer
920 views

What does a black bar across transformer symbol designate?

What does a black bar across a transformer symbol designate? This appears in a power electronics context, and in particular in this case with substituting a DC transformer as an equivalent circuit ...
12
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6answers
4k views

What kind of hardware implements Fourier transform?

I looked around online but I found nothing relevant. It is very difficult for an electronic device to decompose a signal in different frequencies. How this is done at the bare metal level? Any ...
12
votes
6answers
4k views

How To Know If a Fuse Will Work Properly?

I want to know what kind of periodic test we use to test if a current-limiting fuse will normaly open and protect an electronic circuit (a battery charger) if a failure occur (short circuit or over ...
12
votes
4answers
9k views

Why is flyback air gap needed for energy storage?

Why do so many sources say something along the lines "since a flyback transformer stores energy, an air gap is needed"? I have seen this reasoning in textbooks and app notes. I thought air gaps ...
11
votes
5answers
6k views

Will a battery short out when the terminals are directly connected together or will internal resistance save it?

I intended to make a simple electromagnet, then I saw this video where the user is connecting wires together with no resistance at all. I was wondering why it doesn't short out and make the battery ...
11
votes
1answer
2k views

Symbols: Double-arrow circle enclosed “10” on electronic appliances

What does the symbol that says 10 inside the double arrowed circle mean? I have seen a similar symbol on another appliance that had the number 25
11
votes
1answer
726 views

Why do power diodes have a p+ n- n+ construction and why not p+ p- n+?

I've been learning about power diodes and how they differ from low power diodes with the addition of a lightly doped n-type layer. This n-type layer improves the breakdown voltage rating of the ...
10
votes
5answers
3k views

Why/when is AC-DC-AC conversion superior to direct AC-AC conversion?

I am currently studying wind power and the power electronics used for it. In wind power a generator is driven by wind, thus the resulting power is of widely varying frequency and amplitude. The power ...
10
votes
4answers
52k views

How do I find the voltage range for an unknown DC motor?

I have a small unmarked motor with a burned out speed controller board. I'm able to figure out that the motor is a DC motor because it has two wires coming out of it and there's a rectifier on the ...
9
votes
5answers
9k views

What happens if I connect a low voltage rated capacitor to a high voltage?

Given that c=q/v even if I connect it to a higher V, its charge Q may decrease proportionally right? So why should it damage my capacitor? or will the internal electric field get too high and cause ...
9
votes
6answers
2k views

What are the best old electrical appliances to extract electronic components from? [closed]

I would like to build some simple drones and robots which I will be controlling using a microcontroller. Instead of buying expensive brand new components, I prefer to look for old electrical ...
9
votes
7answers
84k views

Why does the USA use 110V and UK use 230-240V?

Why does the USA use 110V and UK use 230-240V? What are the advantages? Explain me with calculation. Why do they use different frequencies like 50Hz, 60Hz? What is the reason?
9
votes
7answers
710 views

Software suggestions for electronic simulations?

I am a beginner in EE engineering and want to use a software where I can analyze signals or even motor speeds, power electronics ect. But the Spice programs looks so boring and detailed for me. Maybe ...
9
votes
3answers
6k views

What is a good power electronics textbook? [closed]

I really want to learn as much as I can about power electronics, switching mode power supplies, and overall analog design. Unfortunately my universities computer engineering program is still ...
9
votes
1answer
2k views

What is this high power switch symbol?

I am a medical physicist, and I program software for MRI scanners as well as develop electronic devices that interact with them. Because of the way MRI works, it is necessary to use very large power ...
8
votes
7answers
860 views

Isn't current flow a wrong term?

In most text books and other electronics material it's said current is flowing through the circuit. Isn't this wrong? As current is flow of charge. Is there anything such as flow of flow of charge?
8
votes
3answers
2k views

Discharging one side of a capacitor?

What I'm asking about is if it's possible to discharge one side of a capacitor. I've found a question about that, but I also found the answers to be a little unclear or questionable. I imagine that ...
8
votes
2answers
479 views

What's the easiest way to prevent a voltage input getting higher than a fixed value?

I just got a DC-DC step-up converter for my laptop, and I want to make double sure in case it malfunctions it will never affect my laptop. I am looking for an extra security device to prevent the ...
8
votes
2answers
885 views

dual of voltage doubler

Voltage doublers, like those close to be one stage of Cockroft-walton multipliers, are well known. They allow to double the voltage of an AC input and can be useful at the output of a transformer for ...
7
votes
2answers
2k views

Does solder expire?

I have some solder that is past the "expiration date" on it. How does solder expire? Is it still good? What happens if I use it? It seems odd that solder could expire, so I'm just looking for some ...
7
votes
1answer
634 views

What does sequences like 1-3, 1-10, 1-3-10 etc in a spectrum analyzer mean?

I have read in a paper explaining spectrum analyzer basic 'When selecting the RBW(resolution BW), there is usually a 1-10 or a 1-3-10 sequence of RBWs available. More RBWs are better because this ...
6
votes
4answers
2k views

What is so special in the power MOSFETS IRFD120 and IRFD110?

I was trying out a hobby project and I was using the IRFD120 and IRFD110 power MOSFETs to control a motor. The transistors worked pretty fine and we simply ran out of them. When I went to buy some ...
6
votes
2answers
838 views

For a MOSFET, does capacitive gate current only flow through to the source?

Everywhere states that a MOSFET has no current at the gate. However, this is not true since, during the time the gate capacitance charges up to reach the certain voltage threshold, the current is ...
6
votes
4answers
24k views

What do you mean by a Wattage of an incandescent bulb?

How do I interpret the wattage of a bulb. For example when it is said that the bulb is rated for 60 W , what does that mean?
6
votes
4answers
2k views

Indicator light circuit

I'm an electrician and my work is to maintain boats. I have a problem. On the boats are sailing lights, and for each sailing light is another light inside the boat that tells you if the sailing ...
6
votes
3answers
2k views

Is it safe to use series polarized capacitors to form non-polarized capacitors to be used for higher rated voltage?

simulate this circuit – Schematic created using CircuitLab It is known that we can use series capacitors to increase rated voltage. But I want to know how far we can push this feature to? ...
6
votes
2answers
559 views

Regarding Ferrite Bead

What is a ferrite bead? How is it different from an inductor? How is it rated? What are its important parameters? What allows me to chose between an inductor or ferrite bead to filter out frequencies ...
6
votes
4answers
544 views

Multimeter measurement

Looking for help with reading my multimeter. I would think by moving from 20 to 200, the decimal place would just shift one place. Why when I switch do I get a reading of 20ma vs 10ma?
6
votes
2answers
7k views

Why is it desirable to inject reactive power into a transmission system?

This website explains the basics of FACTS technologies and how they can be used to exchange active and reactive power with the transmission system, namely: SSSCs - can exchange active and reactive ...
6
votes
2answers
13k views

Calculating a burden resistor for a current transformer

Background: I follow a reference design for a single phase power meter (230 V, max 3 A). The below circuit is to measure current via a current transformer. A current transformer will be ...
6
votes
2answers
825 views

H bridge not switching correctly - Induction heater

I've been working on an induction heater over the last few months and have had varied success. I can drive about 600W through it but as I begin to push past this point it isn't long until one of the ...
6
votes
5answers
1k views

The path of electrons in AC circuit?

I have a question regarding the AC circuit shown below. If we ignore the voltage drop caused by the long cable, I think the device will work and the circuit can be considered as a closed circuit. Now ...
5
votes
2answers
22k views

Role Of Emitter (By Pass) Capacitor

What is the importance of Bypass capacitor of Common-emitter amplifier? Will the gain be reduced when it is removed?
5
votes
4answers
1k views

PWM 1Hz on solid state relay

I'm about to build a pid heating controller with a 1kW heater and a solid state relay. The ESP8266 can go down to 1Hz pwm frequency. So hopefully I can vary the number of active cycles per second, ...
5
votes
3answers
13k views

What is the difference between different types of GND

I would like to know the difference between different types of Grounds like AGND, SGND, Battery Gnd, PGND. Are all the grounds not same? Cant we connect the device to any one of these grounds?
5
votes
3answers
1k views

What does reverse diode on NPN symbol indicate?

Update: A diode in this position is (at least sometimes) referred to as an anti-parallel diode. This term brings up a lot more results on search. I've been scavenging parts from compact fluorescent (...
5
votes
3answers
897 views

Startup problem in boost converter

The figure below is a diagram of a voltage-mode controlled boost converter. I am wondering how experts solve the start-up problem for this converter. Problem: Assume the output voltage is zero at ...
5
votes
4answers
13k views

Parallel MOSFETs and Gate Drive Capability

I'm trying to design a Full-Bridge which can handle upto 330 A (@ 12V). I'm paralleling 3 MOSFETs per leg, and I think I've found a low enough RDS(on) MOSFET to make this somewhat practical. Here's a ...
5
votes
3answers
2k views

Creating positive and negative voltages from a battery

I have a circuit that is usually powered by +9V and -9V (uses two 9 volt batteries), but I am trying to power this from a rechargeable 3.7 V battery. The circuit does not draw much power (can be ...
5
votes
2answers
671 views

What is impedance 'masking' and how it is related to impedance 'matching'?

While reading ECSS-E-ST-20C Standard, I have encountered with a concept named 'impedance mask'. However, I could not find any detailed definition or explanation related to it. In the corresponding ...